You can "cool" a via by using the traces at both ends to remove heat and dump that heat into planes, or simply move the heat away along the traces.
Should the trace on top of Via head off both left and right, you'll get twice as much cooling benefit at the top. Ditto for the bottom
Best case: the trace connects between Planes, with no thermal relief (no soldering expected), then you have EIGHT*2 paths for heat to travel out of that via, and life is nice and cool. Draw a 3 by 3 grid, with via in middle, and
notice the 8 paths (each path is same size as via, so 70 degree Cent/watt) heat will use in exiting the via. The 8 paths produce 70/8 = 9 degree Cent/watt. And you have BOTH planes to remove heat. Now draw 5 by 5, 7 by 7, 9 by 9.
What is thermal resistance from midpoint of the Via (halfway thru the FR-4 epoxy fiberglass? 70degree/2 in each direction, or 35 degrees in each direction. Or 35 in parallel with 35, or 17 degree Cent/watt, if can dump heat into planes on both ends.
Standard 1-ounce-per-foot^2 foil (35 microns, 1.4 mils) has 70 degree C per watt per square of foil, for any size of foil. Get a quadrille pad, and draw some squares